diff --git a/EGkPolyArc.h b/EGkPolyArc.h
index 037803e..53bb15c 100644
--- a/EGkPolyArc.h
+++ b/EGkPolyArc.h
@@ -82,6 +82,7 @@ class PolyArc
       EGK_EXPORT bool GetNextArc( Point3d& ptIni, Point3d& ptFin, double& dBulge) const
                         { return GetNextUArc( nullptr, &ptIni, nullptr, &ptFin, &dBulge) ; }
       EGK_EXPORT bool IsFlat( int& nRank, Point3d& ptCen, Vector3d& vtDir, double dToler = EPS_SMALL) const ;
+      EGK_EXPORT bool Invert( bool bInvertU) ;
 
    private :
       struct UPointB